1. Field of the Invention
The present invention relates to an electromagnetic scanning micro-mirror.
The scanning micro-mirror according to the present invention is applicable to laser printers, confocal microscopes, barcode scanners, scanning displays, and other various sensors, which are designed to scan a light beam, emitted from an optical source, to a predetermined region, such as a one-dimensional (i.e. line) or two-dimensional (i.e. plane) region for forming an image or reading position or image data.
The micro-mirror according to the present invention is also applicable to optical switch devices for freely regulating a path of a reflected light beam, in addition to the above scanning function.
2. Description of the Related Art
Recently, with a development in the technology of optical devices, various technologies for utilizing light as information input/output and information transmission media are on the rise. One of the light utilizing technologies is a method for scanning a light beam emitted from an optical source. A typical application example of such a beam scanning technology includes a barcode scanner, basic-level scanning laser display, or the like.
The beam scanning technology requires different scanning speeds and ranges in accordance with application examples thereof. The main focus of prior art beam scanning is a method for regulating an incident angle, which is formed by a reflective plane of a drive mirror, such as a galvanic mirror or rotating polygon mirror, and an incident light beam. Here, the galvanic mirror is suitable for applications requiring a scanning speed of approximately several hertz, perhaps dozens of hertz, whereas the polygon mirror can achieve a scanning speed of approximately thousands of Hertz.
With a development of several technologies, recently, there has been a ceaseless effort for applying the beam scanning technology to new devices or improving the performance of prior art devices using the beam scanning technology. A good example of this ceaseless effort includes a projection display system featuring a high-resolution primary color re-productivity, head mounted display, laser printer, or the like.
A beam scanning system requiring a high spatial resolution, conventionally, must have a scanning mirror, which is capable of achieving a high scanning speed and a large angular displacement or tilting angle. However, in the case of a prior art method using a polygon mirror, there is a problem in that the polygon mirror is mounted on a drive motor having a high rotating speed, and therefore, a scanning speed, which is proportional to a rotating angular speed of the polygon mirror, depends on the rotating speed of the drive motor. Due to a limited rotating speed of conventional motors, therefore, increasing the scanning speed has a limit, and it is difficult to reduce the consumption of electricity and the volume of the overall system.
In addition, mechanical frictional noise of the drive motor must be essentially eliminated, and a complicated structure makes it difficult to achieve a reduction of manufacturing costs.
FIG. 1 is a schematic view illustrating a scanning device using a polygon mirror in accordance with the prior art. If an input light beam 5 is emitted from an optical source 1, the light beam 5 first passes through an optic 2 that is selected from among various lenses, and then, is reflected by a polygon mirror 3.
With this configuration, as the polygon mirror 3 is rotated by means of a motor 4 mounted underneath thereof, a light beam 6 is reflected by the polygon mirror 3, thereby being scanned in a predetermined direction 8. Here, the scanning direction 8 is determined based on a rotating direction 7 of the polygon mirror 3.
A problem of the above-described prior art scanning device using the polygon mirror 3 is in that it cannot be applied to a high-resolution display, or the like, although it achieves an unidirectional high scanning speed.
On the other hand, another prior art scanning device using a micro-mirror is able to achieve a bidirectional scanning ability and a high scanning speed of dozens of hertz. However, when the scanning device is driven at its operational limit, i.e. the bidirectional high scanning speed, it suffers from a dynamic deflection, causing the micro-mirror to waver during the operation of the scanning device. This is a cause of the distortion of a reflective plane of the micro-mirror, and consequently, the deterioration of a reflected light beam.
Accordingly, in order to achieve a high-performance optical scanning device, it is necessary to select the optimal material and structure of the micro-mirror suitable to restrict the dynamic deflection.
Meanwhile, considering a prior art electrostatic scanning micro-mirror using a vertical comb electrode, it requires a high alignment accuracy of a movable part or rotor and a fixed part or stator in the manufacture thereof. Furthermore, the electrostatic scanning micro-mirror has a difficulty in that a structure thereof must have a high aspect ratio, in order to increase a rotating angle.
Moreover, a movable comb electrode that is attached to a mirror plate and a fixed comb electrode that is located adjacent to the movable comb electrode cause an increase in the dampening of a drive force.